A Harvest Moon

A Harvest Moon. This image was taken with a Canon EOS 5D Mark III on February 14, 2017 with 600.0mm, f/8.0s, 1/500s, ISO 200. Image source: pxhere

If you go out on a clear night when it’s full moon, you may notice how gigantic the Earth’s satellite looks when it’s near the horizon. But, in fact, that moon is the exact same size as every other time as you’ve ever seen it in the sky. You can test this by holding your thumbnail at arm’s length and comparing it to the size of the Moon when it is near the horizon and high in the sky, and you’ll see it doesn’t change size. Photographs of the Moon at different elevations also show that its size remains the same. In fact, it plays a trick on your brain which called the “Moon Illusion”. This illusion has been known since the ancient times, and an explanation of this optical phenomenon is still debated.